Week 15 is the most wonderful time of the year—in the NFL regular season, at least. Among the six must-watch games, there are intense divisional rivalry matchups and potential playoff previews. Two of the marquee games, however, are interconference clashes between championship-rich franchises.

In the Steelers vs. Cowboys and 49ers vs. Patriots matchups, you have franchises that account for 19 of the 46 Super Bowl winners. They are the best games of one great week:

Game/Upset of the Week

San Francisco 49ers at New England Patriots (Sunday, 8:20 p.m. ET, NBC). There is a reason the Patriots are very difficult to beat at home, or anywhere, in December. There is an intimidation factor—and mystique—around the success they have had with Tom Brady leading Bill Belichick’s offense. There’s only one way to fight that history—with fire.

As we’ve seen with the 49ers under Jim Harbaugh, they are tough, physical and fearless on defense. They won’t back down from the challenge of Brady. Look for them to have some success with pressure from their 3-4 defense, which is backed by a better back seven than the Texans have. To get the Patriots’ number, however, the Niners will need to be aggressive on offense.

Forget the strategy of trying to run often with Frank Gore to play keep-away from Brady. The 49ers need to come out firing with Colin Kaepernick, as his big-play ability as a passer and runner is why they picked him to start over Alex Smith. Former Patriot Randy Moss and Super Bowl hero Mario Manningham will stretch the field. The Niners’ tight ends also are tough covers for New England. Expect rookie running back LaMichael James to get some snaps to cause matchup issues.

Brady is the closest thing we have in the NFL to his idol, 49ers legend Joe Montana, but the current Niners makeup makes the difference here. 49ers 33, Patriots 30

Other Game of the Week

Pittsburgh Steelers at Dallas Cowboys (Sunday, 4:25 p.m. ET, CBS). The Cowboys should have top wide receiver Dez Bryant, which will help quarterback Tony Romo. What won’t is the fact that Ben Roethlisberger is his counterpart. Roethlisberger is the more accomplished version of Romo—a mobile, strong-armed passer. Because of Big Ben, the Steelers show mettle on the road and will be eager to put a bad home loss to San Diego behind them. The Cowboys aren’t the best home team in these situations, and Pittsburgh’s running game will set up Roethlisberger to take this game away from Romo in the fourth quarter. Steelers 20, Cowboys 17

AFC Game of the Week

Denver Broncos at Baltimore Ravens (Sunday, 1 p.m. ET, CBS). It seems like Peyton Manning and the Broncos are destined to keep winning all the way to the Super Bowl. But it would be wrong to write off the Ravens after tough losses to the Steelers and Redskins. They are still a very good home team, and with an emotional defensive lift from the return of Ray Lewis and a spark from a new-look offense, expect them to turn in a strong all-around performance. They will need it to cool off the Broncos, and it will be tough, given they must overcome many defensive injuries. With more help from Ray Rice, Joe Flacco will hold up well in his duel with Manning—and a big play by Ed Reed will allow the Ravens to steal this one. Ravens 26, Broncos 24

NFC Game of the Week

Green Bay Packers at Chicago Bears (Sunday, 1 p.m. ET, FOX). Brandon Marshall is ready for a big game against the Packers’ defense, but as we’ve seen the past two weeks, the Bears can’t win with just him carrying their offense. Their line issues continue to limit Jay Cutler, and now the problems have seeped into the running game. Meanwhile, Aaron Rodgers is getting more help from his backfield and has a lot more options in the passing game to methodically move the ball against Chicago’s injury-hampered zone defense. Packers 20, Bears 13

Rematch of the Week

New York Giants at Atlanta Falcons (Sunday, 1 p.m. ET, FOX). The Falcons had a brief 2-0 lead in the teams’ playoff matchup last season, but those were the only points they would score in a frustrating road loss. The Falcons are perfect at home in 2012 and are trying to make sure they stay there for this year’s NFC playoffs. Matt Ryan hasn’t been great in the Georgia Dome this season, but Atlanta’s defense plays a lot better there. Eli Manning and the Giants’ up-and-down offense also are due for an off game. You can bet the Falcons have heard about everyone disrespecting them and will rise up here to prove their worth. Falcons 24, Giants 17

Rebound/Lock of the Week

Indianapolis Colts at Houston Texans (Sunday, 1 p.m. ET, CBS). The Colts are 9-4 but have been outscored by 37 points this season. When they win, it often takes an Andrew Luck-led rally. When they lose, their youth and major defensive holes show up in a big way. The Texans are picking up the pieces from their loss to the Patriots but won’t lose sight of their two big goals: winning the AFC South and going on to lock up the AFC’s top playoff seed. Look for Matt Schaub, Arian Foster and the entire Houston offense to rebound, setting up J.J. Watt and the defense to make the afternoon rough for Luck. Texans 38, Colts 14

Rest of the Week

Jacksonville Jaguars at Miami Dolphins (Sunday, 1 p.m. ET, CBS). The Dolphins have had a positive first season with Joe Philbin and Ryan Tannehill, and are looking to finish strong. They will support their rookie quarterback with good efforts from Reggie Bush and Daniel Thomas against Jacksonville's No. 31-ranked run defense. Former Dolphins starter Chad Henne will lead a valiant Jaguars comeback, but this Sunshine State matchup tips in the favor of South Florida. Dolphins 20, Jaguars 17

Minnesota Vikings at St. Louis Rams (Sunday 1 p.m. ET, FOX). Adrian Peterson will get his rushing yards, as usual, but Jeff Fisher will coach up his defense to limit big gains. Fisher will commit extra defenders to the run, trusting his cornerbacks and middle linebacker James Laurinaitis to handle the Vikings' limited receiving corps. The Rams are quietly No. 2 in the NFL in sacks and won’t allow struggling Vikings quarterback Christian Ponder to win a tight game with slim wild-card hopes on the line. Rams 23, Vikings 20

Tampa Bay Buccaneers at New Orleans Saints (Sunday, 1 p.m. ET, FOX). The Saints got the best possible news with the Bountygate suspensions thrown out, and that should inspire the team to break out of a three-game funk. Look for Drew Brees to get back on track against the Buccaneers' pass defense. The Buccaneers will get their share of big plays from Doug Martin and Vincent Jackson, but it's hard to pick against New Orleans in a Superdome shootout. Saints 34, Buccaneers 27

Washington Redskins at Cleveland Browns (Sunday, 1 p.m. ET, CBS). Robert Griffin III or Kirk Cousins? Given the secretive Mike Shanahan, you can't assume anything about which rookie will quarterback the Redskins. The Redskins’ offense will have to deal with a Browns front that's played very well of late. The real issue in Washington is the defense, and Cleveland's receivers—led by rookie Josh Gordon—are underrated. Look for rookie running back Trent Richardson to also make an impact. Browns 24, Redskins 20

Carolina Panthers at San Diego Chargers (Sunday 4:05 p.m. ET, FOX). It looks like Norv Turner is near the end of the line in San Diego, but he's still coaching his offense well and will be ready to match wits with former Chargers assistants Ron Rivera and Rob Chudzinski, Carolina’s head coach and offensive coordinator. Now that Philip Rivers has found a groove, Ryan Mathews and the Chargers' running game will have success. Cam Newton will stay hot, but he won't get much help on the ground and will fall short in a good duel with Rivers. Chargers 27, Panthers 24

Detroit Lions at Arizona Cardinals (Sunday, 4:05 p.m. ET, FOX). The Cardinals were called out as quitters by Larry Fitzgerald’s father, and that should motivate many of them get off the mat in front of the home crowd. But even if they work hard to put in a strong defensive effort, they can't compensate for their offensive line woes and the return of overmatched rookie quarterback Ryan Lindley to the starting lineup. That takes a lot away from Calvin Johnson vs. Fitzgerald on the marquee. The Lions bring a strong front four and an underrated running game, and that should be enough to grind out their first victory since Week 9. Lions 20, Cardinals 10

Seattle Seahawks vs. Buffalo Bills at Toronto (Sunday 1 p.m. ET, FOX). Seahawks running back Marshawn Lynch, who is powering up at the ideal time, gets to plow through his former team. It won't be at his old stomping grounds in Orchard Park, but rather Toronto. Seattle will feel more at home in Canada and not just because it plays home games near Vancouver. The Seahawks' defense is ablaze after the thrashing of Arizona and will thwart an inconsistent Bills attack. With it, the Space Needle will get spire bragging rights over CN Tower. Seahawks 27, Bills 13

Kansas City Chiefs at Oakland Raiders (Sunday, 4:25 p.m. ET, CBS). There's a good chance both teams will go after a quarterback early in the 2013 draft, and this will determine which gets a better shot at one. Considering the Raiders have a more competent veteran option in Carson Palmer, the Chiefs need one more, as the combination of Matt Cassel and Brady Quinn hasn't worked. Jamaal Charles will provide more great running for Kansas City, but the archrival Raiders now have a healthy Darren McFadden to counter Charles. Raiders 24, Chiefs 20

New York Jets at Tennessee Titans (Monday, 8:30 p.m. ET, ESPN). Just a quick NFL history lesson: The Jets used to be called the Titans, and the Titans used to be called the Oilers. Incredibly, the Jets (6-7) are still alive in the AFC wild-card hunt, and if they can run effectively on an opponent, they usually win. Tennessee will give up chunks of yards to Shonn Greene and Bilal Powell, which will lead to some easier throws for Mark Sanchez. Another Jets strength is pass defense, which they will use to stifle Jake Locker. Jets 26, Titans 19